cut of recursion behind a TruffleBoundary call

Author: timfel

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/statement/AbstractImportNode.java

@@ -78,6 +78,7 @@
 import com.oracle.truffle.api.TruffleLanguage.LanguageReference;
 import com.oracle.truffle.api.dsl.Cached;
 import com.oracle.truffle.api.dsl.Specialization;
+import com.oracle.truffle.api.frame.MaterializedFrame;
 import com.oracle.truffle.api.frame.VirtualFrame;
 import com.oracle.truffle.api.instrumentation.StandardTags;
 import com.oracle.truffle.api.instrumentation.Tag;
@@ -267,11 +268,15 @@ static Object genericImport(VirtualFrame frame, PythonContext context, String na
                     }
                     if (level == 0) {
                         String front = name.substring(0, dotIndex);
-                        // recursion up number of dots in the name
-                        return levelZeroNoFromlist(frame, context, front, null, null, 0,
+                        // recursion up number of dots in the name. we use a boundary call here to avoid PE going recursive
+                        return genericImportBoundary(frame.materialize(), context, front, null, PythonUtils.EMPTY_STRING_ARRAY, 0,
+                                        null, // resolveName is not used with level == 0
                                         raiseNode, // raiseNode only needed if front.length() == 0 at this point
                                         getModuleNode, // used multiple times to get the 'front' module
                                         ensureInitialized,  // used multiple times on the 'front' module
+                                        null, // getPathNode is not used with fromList.length == 0
+                                        null, // callHandleFromlist not used with fromList.length == 0
+                                        null, // factory not used with fromList.length == 0
                                         findAndLoad); // used multiple times, but always to call the exact same function
                     } else {
                         int cutoff = nameLength - dotIndex;
@@ -297,6 +302,27 @@ static Object genericImport(VirtualFrame frame, PythonContext context, String na
                 }
             }
         }
+
+        @TruffleBoundary
+        static Object genericImportBoundary(MaterializedFrame frame, PythonContext context, String name, Object globals, String[] fromList, int level,
+                        ResolveName resolveName,
+                        PRaiseNode raiseNode,
+                        PyDictGetItem getModuleNode,
+                        EnsureInitializedNode ensureInitialized,
+                        PyObjectLookupAttr getPathNode,
+                        PyObjectCallMethodObjArgs callHandleFromlist,
+                        PythonObjectFactory factory,
+                        FindAndLoad findAndLoad) {
+            return genericImport(frame, context, name, globals, fromList, level,
+                            resolveName,
+                            raiseNode,
+                            getModuleNode,
+                            ensureInitialized,
+                            getPathNode,
+                            callHandleFromlist,
+                            factory,
+                            findAndLoad);
+        }
     }
 
     /**